Ganglioside GT1B and melatonin inhibit brain mitochondrial DNA damage and seizures induced by kainic acid in mice

Therapeutic Strategies to Ameliorate Neuronal Damage in Epilepsy by Regulating Oxidative Stress, Mitochondrial Dysfunction, and Neuroinflammation

Epilepsy is a central nervous system disorder involving spontaneous and recurring seizures that affects 50 million individuals globally. Because approximately one-third of patients with epilepsy do not respond to drug therapy, the development of new therapeutic strategies against epilepsy could be beneficial. Oxidative stress and mitochondrial dysfunction are frequently observed in epilepsy. Additionally, neuroinflammation is increasingly understood to contribute to the pathogenesis of epilepsy. Mitochondrial dysfunction is also recognized for its contributions to neuronal excitability and apoptosis, which can lead to neuronal loss in epilepsy. This review focuses on the roles of oxidative damage, mitochondrial dysfunction, NAPDH oxidase, the blood-brain barrier, excitotoxicity, and neuroinflammation in the development of epilepsy. We also review the therapies used to treat epilepsy and prevent seizures, including anti-seizure medications, anti-epileptic drugs, anti-inflammatory therapies, and antioxidant therapies. In addition, we review the use of neuromodulation and surgery in the treatment of epilepsy. Finally, we present the role of dietary and nutritional strategies in the management of epilepsy, including the ketogenic diet and the intake of vitamins, polyphenols, and flavonoids. By reviewing available interventions and research on the pathophysiology of epilepsy, this review points to areas of further development for therapies that can manage epilepsy.

Serum Levels of Neuropeptides in Epileptic Encephalopathy With Spike-and-Wave Activation in Sleep

BACKGROUND

Epileptic encephalopathy with spike-and-wave activation in sleep (EE-SWAS) is a syndrome of childhood, characterized by diffuse or generalized spike-wave activity in electroencephalography during non-rapid eye movement sleep. Neuropeptides have been demonstrated in several studies to function in the sleep-wake cycle and display convulsant and anticonvulsant features. In this study, we aimed to investigate the relationship between EE-SWAS and neuropeptides such as dynorphin, galanin, ghrelin, leptin, melatonin, and orexin.

METHODS

This multicenter study was conducted from July 2019 to January 2021. There were three groups: Group 1 contained patients with EE-SWAS. Group 2 consisted of patients with self-limited focal epilepsy of childhood (SeLFE), and group 3 was the control group. Levels of neuropeptides were compared in the sera of these three groups.

RESULTS

There were 59 children aged between four and 15 years. Group 1 contained 14 children, group 2 contained 24 children, and group 3 contained 21 children. The level of leptin is higher and the level of melatonin is lower in group 1 than in group 3 (P = 0.01 and P = 0.005, respectively). In group 3, the level of orexin was lower than in both groups 2 and 3 (P = 0.01 and P = 0.01).

CONCLUSIONS

These data show that the level of leptin was higher and the level of melatonin was lower in patients with EE-SWAS than in the control group. Furthermore, patients with EE-SWAS had lower orexin levels than both the control group and patients with SeLFE. Further research is required to understand the potential role of these neuropeptides in the pathophysiology of EE-SWAS.

Emerging perspectives on mitochondrial dysfunctioning and inflammation in epileptogenesis

INTRODUCTION

Mitochondrial dysfunction is a common denominator of neuroinflammation recognized by neuronal oxidative stress-mediated apoptosis that is well recognized by common intracellular molecular pathway-interlinked neuroinflammation and mitochondrial oxidative stress, a feature of epileptogenesis. In addition, the neuronal damage in the epileptic brain corroborated the concept of brain injury-mediated neuroinflammation, further providing an interlink between inflammation, mitochondrial dysfunction, and oxidative stress in epilepsy.

MATERIALS AND METHODS

A systematic literature review of Bentham, Scopus, PubMed, Medline, and EMBASE (Elsevier) databases was carried out to provide evidence of preclinical and clinically used drugs targeting such nuclear, cytosolic, and mitochondrial proteins suggesting that the correlation of mechanisms linked to neuroinflammation has been elucidated in the current review. Despite that, the evidence of elevated levels of inflammatory mediators and pro-apoptotic protein levels can provide the correlation of inflammatory responses often concerned with hyperexcitability attributing to the fact that mitochondrial redox mechanisms and higher susceptibilities to neuroinflammation result from repetitive recurring epileptic seizures. Therefore, providing an understanding of seizure-induced pathological changes read by activating neuroinflammatory cascades like NF-kB, RIPK, MAPK, ERK, JNK, and JAK-STAT signaling further related to mitochondrial damage promoting hyperexcitability.

CONCLUSION

The current review highlights the further opportunity for establishing therapeutic interventions underlying the apparent correlation of neuroinflammation mediated mitochondrial oxidative stress might contribute to common intracellular mechanisms underlying a future prospective of drug treatment targeting mitochondrial dysfunction linked to the neuroinflammation in epilepsy.

Antioxidants Targeting Mitochondrial Oxidative Stress: Promising Neuroprotectants for Epilepsy

Mitochondria are major sources of reactive oxygen species (ROS) within the cell and are especially vulnerable to oxidative stress. Oxidative damage to mitochondria results in disrupted mitochondrial function and cell death signaling, finally triggering diverse pathologies such as epilepsy, a common neurological disease characterized with aberrant electrical brain activity. Antioxidants are considered as promising neuroprotective strategies for epileptic condition via combating the deleterious effects of excessive ROS production in mitochondria. In this review, we provide a brief discussion of the role of mitochondrial oxidative stress in the pathophysiology of epilepsy and evidences that support neuroprotective roles of antioxidants targeting mitochondrial oxidative stress including mitochondria-targeted antioxidants, polyphenols, vitamins, thiols, and nuclear factor E2-related factor 2 (Nrf2) activators in epilepsy. We point out these antioxidative compounds as effectively protective approaches for improving prognosis. In addition, we specially propose that these antioxidants exert neuroprotection against epileptic impairment possibly by modulating cell death interactions, notably autophagy-apoptosis, and autophagy-ferroptosis crosstalk.

Gangliosides in the Brain: Physiology, Pathophysiology and Therapeutic Applications

Gangliosides are glycosphingolipids highly abundant in the nervous system, and carry most of the sialic acid residues in the brain. Gangliosides are enriched in cell membrane microdomains ("lipid rafts") and play important roles in the modulation of membrane proteins and ion channels, in cell signaling and in the communication among cells. The importance of gangliosides in the brain is highlighted by the fact that loss of function mutations in ganglioside biosynthetic enzymes result in severe neurodegenerative disorders, often characterized by very early or childhood onset. In addition, changes in the ganglioside profile (i.e., in the relative abundance of specific gangliosides) were reported in healthy aging and in common neurological conditions, including Huntington's disease (HD), Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), stroke, multiple sclerosis and epilepsy. At least in HD, PD and in some forms of epilepsy, experimental evidence strongly suggests a potential role of gangliosides in disease pathogenesis and potential treatment. In this review, we will summarize ganglioside functions that are crucial to maintain brain health, we will review changes in ganglioside levels that occur in major neurological conditions and we will discuss their contribution to cellular dysfunctions and disease pathogenesis. Finally, we will review evidence of the beneficial roles exerted by gangliosides, GM1 in particular, in disease models and in clinical trials.

Intracellular G-actin targeting of peripheral sensory neurons by the multifunctional engineered protein C2C confers relief from inflammatory pain

The engineered multifunctional protein C2C was tested for control of sensory neuron activity by targeted G-actin modification. C2C consists of the heptameric oligomer, C2II-CI, and the monomeric ribosylase, C2I. C2C treatment of sensory neurons and SH-SY5Y cells in vitro remodeled actin and reduced calcium influx in a reversible manner. C2C prepared using fluorescently labeled C2I showed selective in vitro C2I delivery to primary sensory neurons but not motor neurons. Delivery was dependent on presence of both C2C subunits and blocked by receptor competition. Immunohistochemistry of mice treated subcutaneously with C2C showed colocalization of subunit C2I with CGRP-positive sensory neurons and fibers but not with ChAT-positive motor neurons and fibers. The significance of sensory neuron targeting was pursued subsequently by testing C2C activity in the formalin inflammatory mouse pain model. Subcutaneous C2C administration reduced pain-like behaviors by 90% relative to untreated controls 6 h post treatment and similarly to the opioid buprenorphene. C2C effects were dose dependent, equally potent in female and male animals and did not change gross motor function. One dose was effective in 2 h and lasted 1 week. Administration of C2I without C2II-CI did not reduce pain-like behavior indicating its intracellular delivery was required for behavioral effect.

Neuroinflammation impact in epileptogenesis and new treatment strategy

Epilepsy is considered a major serious chronic neurological disorder, characterized by recurrent seizures. It is usually associated with a history of a lesion in the nervous system. Irregular activation of inflammatory molecules in the injured tissue is an important factor in the development of epilepsy. It is unclear how the imbalanced regulation of inflammatory mediators contributes to epilepsy. A recent research goal is to identify interconnected inflammation pathways which may be involved in the development of epilepsy. The clinical use of available antiepileptic drugs is often restricted by their limitations, incidence of several side effects, and drug interactions. So development of new drugs, which modulate epilepsy through novel mechanisms, is necessary. Alternative therapies and diet have recently reported positive treatment outcomes in epilepsy. Vitamin D (Vit D) has shown prophylactic and therapeutic potential in different neurological disorders. So, the aim of current study was to review the associations between different brain inflammatory mediators and epileptogenesis, to strengthen the idea that targeting inflammatory pathway may be an effective therapeutic strategy to prevent or treat epilepsy. In addition, neuroprotective effects and mechanisms of Vit D in clinical and preclinical studies of epilepsy were reviewed.

Intranasal Administration of Insulin and Gangliosides Improves Spatial Memory in Rats with Neonatal Type 2 Diabetes Mellitus

We analyzed the effects of intranasal administration of insulin (0.48 U/rat) and gangliosides (6 mg/kg) on spatial memory in rats with the neonatal model of the type 2 diabetes mellitus. The development of diabetes was verified by the glucose tolerance test. Insulin and gangliosides improved training and reversal training in diabetic rats in a modified version of Morris water maze test and reduced the time of finding the hidden platform. High effectiveness of intranasal administration of gangliosides to animals for the normalization of cognitive functions was shown for the first time. The effects of insulin and gangliosides were similar during training, but during reversal training, gangliosides were more effective. At the same time, intranasally administered insulin, unlike gangliosides, partially normalized glucose tolerance in rats with type 2 diabetes mellitus.

Exogenous Ganglioside GT1b Enhances Porcine Oocyte Maturation, Including the Cumulus Cell Expansion and Activation of EGFR and ERK1/2 Signaling

Ganglioside GT1b is well-known for its role in cytokine production and in activating epidermal growth factor receptor (EGFR)-mediated signaling pathways in cancer cells. However, there are no reports that clearly elucidate the role of GT1b in EGFR-mediated signaling pathways in porcine oocytes during the process of in vitro maturation (IVM). In this study, we investigated the role of GT1b in EGFR-mediated activation of the ERK1/2 pathway in porcine cumulus-oocyte complexes (COCs) at 44 h of IVM. Our data show that expression of the ST3GAL2 protein significantly increased in porcine COCs at 44 h irrespective of treatment with EGF. Meiotic maturation and mRNA levels of factors (HAS2, TNFAIP6, and PTX3) related to cumulus cell expansion significantly increased in COCs treated with 2 μM GT1b during IVM in the absence of EGF. They also increased in COCs treated with EGF/GT1b as compared to that in the other groups. Interestingly, protein levels of EGFR, phospho-EGFR, ERK1/2, and phospho-ERK1/2 dramatically increased in COCs treated with EGF/GT1b. Moreover, the rate of fertilization and the developmental competence of blastocyst were significantly higher in EGF/GT1b-treated COCs. Taken together, these results suggest that exogenous GT1b improves meiotic maturation and cumulus cell expansion in porcine COCs via activation of EGFR-mediated ERK1/2 signaling.

Effects of Gangliosides on Spermatozoa, Oocytes, and Preimplantation Embryos

Gangliosides are sialic acid-containing glycosphingolipids, which are the most abundant family of glycolipids in eukaryotes. Gangliosides have been suggested to be important lipid molecules required for the control of cellular procedures, such as cell differentiation, proliferation, and signaling. GD1a is expressed in interstitial cells during ovarian maturation in mice and exogenous GD1a is important to oocyte maturation, monospermic fertilization, and embryonic development. In this context, GM1 is known to influence signaling pathways in cells and is important in sperm-oocyte interactions and sperm maturation processes, such as capacitation. GM3 is expressed in the vertebrate oocyte cytoplasm, and exogenously added GM3 induces apoptosis and DNA injury during in vitro oocyte maturation and embryogenesis. As a consequence of this, ganglioside GT1b and GM1 decrease DNA fragmentation and act as H2O2 inhibitors on germ cells and preimplantation embryos. This review describes the functional roles of gangliosides in spermatozoa, oocytes, and early embryonic development.

Melatonin and its metabolites as chemical agents capable of directly repairing oxidized DNA

Oxidative stress mediates chemical damage to DNA yielding a wide variety of products. In this work, the potential capability of melatonin and several of its metabolites to repair directly (chemically) oxidative lesions in DNA was explored. It was found that all the investigated molecules are capable of repairing guanine-centered radical cations by electron transfer at very high rates, that is, diffusion-limited. They are also capable of repairing C-centered radicals in the sugar moiety of 2'-deoxyguanosine (2dG) by hydrogen atom transfer. Although this was identified as a rather slow process, with rate constants ranging from 1.75 to 5.32 × 10²  M^-1 s^-1 , it is expected to be fast enough to prevent propagation of the DNA damage. Melatonin metabolites 6-hydroxymelatonin (6OHM) and 4-hydroxymelatonin (4OHM) are also predicted to repair OH adducts in the imidazole ring. In particular, the rate constants corresponding to the repair of 8-OH-G adducts were found to be in the order of 10⁴  M^-1 s^-1 and are assisted by a water molecule. The results presented here strongly suggest that the role of melatonin in preventing DNA damage might be mediated by its capability, combined with that of its metabolites, to directly repair oxidized sites in DNA through different chemical routes.

Melatonin: A Versatile Protector against Oxidative DNA Damage

Oxidative damage to DNA has important implications for human health and has been identified as a key factor in the onset and development of numerous diseases. Thus, it is evident that preventing DNA from oxidative damage is crucial for humans and for any living organism. Melatonin is an astonishingly versatile molecule in this context. It can offer both direct and indirect protection against a wide variety of damaging agents and through multiple pathways, which may (or may not) take place simultaneously. They include direct antioxidative protection, which is mediated by melatonin's free radical scavenging activity, and also indirect ways of action. The latter include, at least: (i) inhibition of metal-induced DNA damage; (ii) protection against non-radical triggers of oxidative DNA damage; (iii) continuous protection after being metabolized; (iv) activation of antioxidative enzymes; (v) inhibition of pro-oxidative enzymes; and (vi) boosting of the DNA repair machinery. The rather unique capability of melatonin to exhibit multiple neutralizing actions against diverse threatening factors, together with its low toxicity and its ability to cross biological barriers, are all significant to its efficiency for preventing oxidative damage to DNA.

Antiepileptogenic and Neuroprotective Effects of Pergularia daemia on Pilocarpine Model of Epilepsy

In this study, we investigated antiepileptogenic and neuroprotective effects of the aqueous extract of Pergularia daemia roots (PDR) using in vivo and in vitro experimental models. In in vivo studies, status epilepticus caused by pilocarpine injection triggers epileptogenesis which evolves during about 1–2 weeks. After 2 h of status epilepticus, mice were treated during the epileptogenesis period for 7 days with sodium valproate and vitamin C (standards which demonstrated to alter epileptogenesis), or Pergularia daemia. The animals were then, 1 week after status epilepticus, challenged with acute pentylenetetrazole (PTZ) administration to test behaviorally the susceptibility to a convulsant agent of animals treated or not with the plan extract. Memory was assessed after PTZ administration in the elevated plus maze and T-maze paradigms at 24 and 48 h. Antioxidant and acetylcholinesterase activities were determined in the hippocampus after sacrifice, in vitro studies were conducted using embryonic rat primary cortical cultures exposed to L-glutamate. Cell survival rate was measured and apoptotic and necrotic cell death determined. The results showed that chronic oral administration of PDR significantly and dose-dependently increased the latency to myoclonic jerks, clonic seizures and generalized tonic–clonic seizures, and the seizure score. In addition, PDR at all doses (from 4.9 to 49 mg/kg) significantly decreased the initial and retention transfer latencies in the elevated plus maze. Interestingly PDR at the same doses significantly increased the time spent and the number of entries in T-maze novel arm. PDR significantly increased the activities of acetylcholinesterase and antioxidant enzymes superoxide dismutase, catalase, and total glutathione and proteins, and decreased malondialdehyde level. Furthermore, PDR increased viability rate of primary cortical neurons after L-glutamate-induced excitotoxicity, in a dose dependent manner. Altogether these results suggest that PDR has antiepileptogenic and neuroprotective effects, which could be mediated by antioxidant and antiapoptotic activities.

Effect of ganglioside GT1b on the in vitro maturation of porcine oocytes and embryonic development

Ganglioside is an acidic glycosphingolipid with sialic acids residues. This study was performed to investigate the effect and mechanism of ganglioside GT1b in porcine oocytes in the process of in vitro maturation (IVM) and preimplantation development. Metaphase II (MII) rates were significantly (P < 0.05) different between the control group and the 5 nM GT1b treatment group. Intracellular glutathione (GSH) levels in oocytes matured with 5 nM and 20 nM and GT1b decreased significantly (P < 0.05). The 10 nM group showed a significant (P < 0.05) decrease in intracellular reactive oxygen species (ROS) levels compared with the control group. Subsequently, the level of intracellular Ca(2+) in oocytes treated with different concentrations of GT1b was measured. Intracellular Ca(2+) was significantly (P < 0.05) increased with a higher concentration of GT1b in a dose-dependent manner. Real-time PCR was performed and showed that the expression of bradykinin 2 receptor (B2R) and calcium/calmodulin-dependent protein kinase II delta (CaMKIIδ) in cumulus cells was significantly (P < 0.05) decreased in the 20 nM GT1b treatment group. Treatment with 5 nM GT1b significantly (P < 0.05) decreased the expression of CaMKIIδ. In oocytes, treatment with 5 nM GT1b significantly (P < 0.05) decreased CaMKIIγ and POU5F1 (POU domain, class 5, transcription factor 1). However, treatment with 20 nM GT1b significantly (P < 0.05) increased the expression of POU5F1. Finally, embryonic developmental data showed no significant differences in the two experiments (parthenogenesis and in vitro fertilization). In conclusion, the results of the present study indicated that GT1b plays an important role in increasing the nuclear maturation rate and decreasing the intracellular ROS levels during IVM. However, GT1b inhibited maturation of the cytoplasm by maintaining intracellular Ca(2+) in the process of oocyte maturation regardless of the cell cycle stage. Therefore, GT1b is thought to act on another mechanism that controls intracellular Ca(2+).

The potential physiological crosstalk and interrelationship between two sovereign endogenous amines, melatonin and homocysteine

The antioxidant melatonin and the non-proteinogenic excitotoxic amino acid homocysteine (Hcy) are very distinct but related reciprocally to each other in their mode of action. The elevated Hcy level has been implicated in several disease pathologies ranging from cardio- and cerebro-vascular diseases to neurodegeneration owing largely to its free radical generating potency. Interestingly, melatonin administration potentially normalizes the elevated Hcy level, thereby protecting the cells from the undesired Hcy-induced excitotoxicity and cell death. However, the exact mechanism and between them remain obscure. Through literature survey we have found an indistinct but a vital link between melatonin and Hcy i.e., the existence of reciprocal regulation between them, and this aspect has been thoroughly described herein. In this review, we focus on all the possibilities of co-regulation of melatonin and Hcy at the level of their production and metabolism both in basal and in pathological conditions, and appraised the potential of melatonin in ameliorating homocysteinemia-induced cellular stresses. Also, we have summarized the differential mode of action of melatonin and Hcy on health and disease states.

Antioxidants as a preventive treatment for epileptic process: a review of the current status

Epilepsy is known as one of the most frequent neurological diseases, characterized by an enduring predisposition to generate epileptic seizures. Oxidative stress is believed to directly participate in pathways leading to neurodegeneration, which serves as the most important propagating factor, leading to the epileptic condition and cognitive decline. Moreover, there is also a growing body of evidence showing the disturbance of antioxidant system balance and consequently increased production of reactive species in patients with epilepsy. A meta-analysis, conducted in the present review confirms an association between epilepsy and increased lipid peroxidation. Furthermore, it was also shown that some of the antiepileptic drugs could potentially be responsible for additionally increased lipid peroxidation. Therefore, it is reasonable to propose that during the epileptic process neuroprotective treatment with antioxidants could lead to less sever structural damages, reduced epileptogenesis and milder cognitive deterioration. To evaluate this hypothesis studies investigating the neuroprotective therapeutic potential of various antioxidants in cells, animal seizure models and patients with epilepsy have been reviewed. Numerous beneficial effects of antioxidants on oxidative stress markers and in some cases also neuroprotective effects were observed in animal seizure models. However, despite these encouraging results, till now only a few antioxidants have been further applied to patients with epilepsy as an add-on therapy. Based on the several positive findings in animal models, a strong need for more carefully planned, randomized, double-blind, cross-over, placebo-controlled clinical trials for the evaluation of antioxidants efficacy in patients with epilepsy is warranted.

GM1 ganglioside activates ERK1/2 and Akt downstream of Trk tyrosine kinase and protects PC12 cells against hydrogen peroxide toxicity

Ganglioside GM1 at micro- and nanomolar concentrations was shown to increase the viability of pheochromocytoma PC12 cells exposed to hydrogen peroxide and diminish the accumulation of reactive oxygen species and oxidative inactivation of Na(+),K(+)-ATPase, the effects of micromolar GM1 being more pronounced than those of nanomolar GM1. These effects of GM1 were abolished by Trk receptor tyrosine kinase inhibitor and diminished by MEK1/2, phosphoinositide 3-kinase and protein kinase C inhibitors. Hydrogen peroxide activates Trk tyrosine kinase; Akt and ERK1/2 are activated downstream of this protein kinase. GM1 was found to activate Trk receptor tyrosine kinase in PC12 cells. GM1 (100 nM and 10 µM) increased the basal activity of Akt, but did not change Akt activity in cells exposed to hydrogen peroxide. Basal ERK1/2 activity in PC12 cells was increased by GM1 at a concentration of 10 µM, but not at nanomolar concentrations. Activation of ERK1/2 by hydrogen peroxide was enhanced by GM1 at a concentration of 10 µM and to a lesser extent at a concentration of 100 nM. Thus, the protective and metabolic effects of GM1 ganglioside on PC12 cells exposed to hydrogen peroxide appear to depend on the activation of Trk receptor tyrosine kinase and downstream activation of Akt and ERK1/2.

Protective effects of exogenous gangliosides on ROS-induced changes in human spermatozoa

This article summarizes the available evidence on the efficacy of gangliosides to reduce the degree of reactive oxygen species (ROS)-mediated damage. The antioxidative efficacy of exogenous gangliosides in protecting different cells encouraged us to examine their ability to protect human spermatozoa. Gangliosides are sialic acid-containing glycosphingolipids with strong amphiphilic character due to the bulky headgroup made of several sugar rings with sialic acid residues and the double-tailed hydrophobic lipid moiety. The amphiphilicity of gangliosides allows them to exist as micelles in aqueous media when they are present at a concentration above their critical micellar concentration. The protective effect of ganglioside micelles on spermatozoa is believed to stem from their ability to scavenge free radicals and prevent their damaging effects. In our study, we particularly focused our attention on the protective effect of ganglioside micelles on DNA in human spermatozoa exposed to cryopreservation. The results indicate that ganglioside micelles can modulate the hydrophobic properties of the sperm membrane to increase tolerance to DNA fragmentation, thus protecting the DNA from cryopreservation-induced damage. Further actions of ganglioside micelles, which were documented by biochemical and biophysical studies, included (i) the modulation of superoxide anion generation by increasing the diffusion barrier for membrane events responsible for signal translocation to the interior of the cell; (ii) the inhibition of iron-catalysed hydroxyl radical formation due to the iron chelation potential of gangliosides; and (iii) inhibition of hydrogen peroxide diffusion across the sperm membrane.

The role of reactive species in epileptogenesis and influence of antiepileptic drug therapy on oxidative stress

Epilepsy is considered one of the most common neurological disorders. The focus of this review is the acquired form of epilepsy, with the development process consisting of three major phases, the acute injury phase, the latency epileptogenesis phase, and the phase of spontaneous recurrent seizures. Nowadays, an increasing attention is paid to the possible interrelationship between oxidative stress resulting in disturbance of physiological signalling roles of calcium and free radicals in neuronal cells and mitochondrial dysfunction, cell damage, and epilepsy. The positive stimulation of mitochondrial calcium signals by reactive oxygen species and increased reactive oxygen species generation resulting from increased mitochondrial calcium can lead to a positive feedback loop. We propose that calcium can pose both, physiological and pathological effects of mitochondrial function, which can lead in neuronal cell death and consequent epileptic seizures. Various antiepileptic drugs may impair the endogenous antioxidative ability to prevent oxidative stress. Therefore, some antiepileptic drugs, especially from the older generation, may trigger oxygen-dependent tissue injury. The prooxidative effects of these antiepileptic drugs might lead to enhancement of seizure activity, resulting in loss of their efficacy or apparent functional tolerance and undesired adverse effects. Additionally, various reactive metabolites of antiepileptic drugs are capable of covalent binding to macromolecules which may lead to deterioration of the epileptic seizures and systemic toxicity. Since neuronal loss seems to be one of the major neurobiological abnormalities in the epileptic brain, the ability of antioxidants to attenuate seizure generation and the accompanying changes in oxidative burden, further support an important role of antioxidants as having a putative antiepileptic potential.

Roles of gangliosides in mouse embryogenesis and embryonic stem cell differentiation

Gangliosides have been suggested to play important roles in various functions such as adhesion, cell differentiation, growth control, and signaling. Mouse follicular development, ovulation, and luteinization during the estrous cycle are regulated by several hormones and cell-cell interactions. In addition, spermatogenesis in seminiferous tubules of adult testes is also regulated by several hormones, including follicle-stimulating hormone (FSH) and luteinizing hormone (LH) and cell-cell interactions. The regulation of these processes by hormones and cell-cell interactions provides evidence for the importance of surface membrane components, including gangliosides. During preimplantation embryo development, a mammalian embryo undergoes a series of cleavage divisions whereby a zygote is converted into a blastocyst that is sufficiently competent to be implanted in the ma ternal uterus and continue its development. Mouse embryonic stem (mES) cells are pluripotent cells derived from mouse embryo, specifically, from the inner cell mass of blastocysts. Differentiated neuronal cells are derived from mES cells through the formation of embryonic bodies (EBs). EBs recapitulate many aspects of lineage-specific differentiation and temporal and spatial gene expression patterns during early embryogenesis. Previous studies on ganglioside expression during mouse embryonic development (including during in vitro fertilization, ovulation, spermatogenesis, and embryogenesis) reported that gangliosides were expressed in both undifferentiated and differentiated (or differentiating) mES cells. In this review, we summarize some of the advances in our understanding of the functional roles of gangliosides during the stages of mouse embryonic development, including ovulation, spermatogenesis, and embryogenesis, focusing on undifferentiated and differentiated mES cells (neuronal cells).

Nickel exposure induces oxidative damage to mitochondrial DNA in Neuro2a cells: the neuroprotective roles of melatonin

Recent studies suggest that oxidative stress and mitochondrial dysfunction play important roles in the neurotoxicity of nickel. Because mitochondrial DNA (mtDNA) is highly vulnerable to oxidative stress and melatonin can efficiently protect mtDNA against oxidative damage in various pathological conditions, the aims of this study were to determine whether mtDNA oxidative damage was involved in the neurotoxicity of nickel and to assay the neuroprotective effects of melatonin in mtDNA. In this study, we exposed mouse neuroblastoma cell lines (Neuro2a) to different concentrations of nickel chloride (NiCl(2), 0.125, 0.25, and 0.5 mm) for 24 hr. We found that nickel significantly increased reactive oxygen species (ROS) production and mitochondrial superoxide levels. In addition, nickel exposure increased mitochondrial 8-hydroxyguanine (8-OHdG) content and reduced mtDNA content and mtDNA transcript levels. Consistent with this finding, nickel was found to destroy mtDNA nucleoid structure and decrease protein levels of Tfam, a key protein component for nucleoid organization. However, all the oxidative damage to mtDNA induced by nickel was efficiently attenuated by melatonin pretreatment. Our results suggest that oxidative damage to mtDNA may account for the neurotoxicity of nickel. Melatonin has great pharmacological potential in protecting mtDNA against the adverse effects of nickel in the nervous system.

Role of oxidative stress in epileptic seizures

Oxidative stress resulting from excessive free-radical release is likely implicated in the initiation and progression of epilepsy. Therefore, antioxidant therapies aimed at reducing oxidative stress have received considerable attention in epilepsy treatment. However, much evidence suggests that oxidative stress does not always have the same pattern in all seizures models. Thus, this review provides an overview aimed at achieving a better understanding of this issue. We summarize work regarding seizure models (i.e., genetic rat models, kainic acid, pilocarpine, pentylenetetrazol, and trimethyltin), oxidative stress as an etiologic factor in epileptic seizures (i.e., impairment of antioxidant systems, mitochondrial dysfunction, involvement of redox-active metals, arachidonic acid pathway activation, and aging), and antioxidant strategies for seizure treatment. Combined, this review highlights pharmacological mechanisms associated with oxidative stress in epileptic seizures and the potential for neuroprotection in epilepsy that targets oxidative stress and is supported by effective antioxidant treatment.

Melatonin in experimental seizures and epilepsy

Although melatonin is approved only for the treatment of jet-lag syndrome and some types of insomnia, clinical data suggest that it is effective in the adjunctive therapy of osteoporosis, cataract, sepsis, neurodegenerative diseases, hypertension, and even cancer. Melatonin also modulates the electrical activity of neurons by reducing glutamatergic and enhancing GABA-ergic neurotransmission. The indoleamine may also be metabolized to kynurenic acid, an endogenous anticonvulsant. Finally, the hormone and its metabolites act as free radical scavengers and antioxidants. The vast majority of experimental data indicates anticonvulsant properties of the hormone. Melatonin inhibited audiogenic and electrical seizures, as well as reduced convulsions induced by pentetrazole, pilocarpine, L-cysteine and kainate. Only a few studies have shown direct or indirect proconvulsant effects of melatonin. For instance, melatonin enhanced low Mg2+-induced epileptiform activity in the hippocampus, whereas melatonin antagonists delayed the onset of pilocarpine-induced seizures. However, the relatively high doses of melatonin required to inhibit experimental seizures can induce some undesired effects (e.g., cognitive and motor impairment and decreased body temperature). In humans, melatonin may attenuate seizures, and it is most effective in the treatment of juvenile intractable epilepsy. Its additional benefits include improved physical, emotional, cognitive, and social functions. On the other hand, melatonin has been shown to induce electroencephalographic abnormalities in patients with temporal lobe epilepsy and increase seizure activity in neurologically disabled children. The hormone showed very low toxicity in clinical practice. The reported adverse effects (nightmares, hypotension, and sleep disorders) were rare and mild. However, more placebo-controlled, double-blind randomized clinical trials are needed to establish the usefulness of melatonin in the adjunctive treatment of epilepsy.

Sesamin ameliorates oxidative stress and mortality in kainic acid-induced status epilepticus by inhibition of MAPK and COX-2 activation

BACKGROUND

Kainic acid (KA)-induced status epilepticus (SE) was involved with release of free radicals. Sesamin is a well-known antioxidant from sesame seeds and it scavenges free radicals in several brain injury models. However the neuroprotective mechanism of sesamin to KA-induced seizure has not been studied.

METHODS

Rodents (male FVB mice and Sprague-Dawley rats) were fed with sesamin extract (90% of sesamin and 10% sesamolin), 15 mg/kg or 30 mg/kg, for 3 days before KA subcutaneous injection. The effect of sesamin on KA-induced cell injury was also investigated on several cellular pathways including neuronal plasticity (RhoA), neurodegeneration (Caspase-3), and inflammation (COX-2) in PC12 cells and microglial BV-2 cells.

RESULTS

Treatment with sesamin extract (30 mg/kg) significantly increased plasma α-tocopherol level 50% and 55.8% from rats without and with KA treatment, respectively. It also decreased malondialdehyde (MDA) from 145% to 117% (p=0.017) and preserved superoxide dismutase from 55% of the vehicle control mice to 81% of sesamin-treated mice, respectively to the normal levels (p=0.013). The treatment significantly decreased the mortality from 22% to 0% in rats. Sesamin was effective to protect PC12 cells and BV-2 cells from KA-injury in a dose-dependent manner. It decreased the release of Ca2+, reactive oxygen species, and MDA from PC12 cells. Western blot analysis revealed that sesamin significantly reduced ERK1/2, p38 mitogen-activated protein kinases, Caspase-3, and COX-2 expression in both cells and RhoA expression in BV-2 cells. Furthermore, Sesamin was able to reduce PGE2 production from both cells under KA-stimulation.

CONCLUSIONS

Taken together, it suggests that sesamin could protect KA-induced brain injury through anti-inflammatory and partially antioxidative mechanisms.

Mitochondrial dysfunction and oxidative stress: a contributing link to acquired epilepsy?

Mitochondrial dysfunction and oxidative stress contribute to several neurologic disorders and have recently been implicated in acquired epilepsies such as temporal lobe epilepsy (TLE). Acquired epilepsy is typically initiated by a brain injury followed by a "latent period" whereby molecular, biochemical and other cellular alterations occur in the brain leading to chronic epilepsy. Mitochondrial dysfunction and oxidative stress are emerging as factors that not only occur acutely as a result of precipitating injuries such as status epilepticus (SE), but may also contribute to epileptogenesis and chronic epilepsy. Mitochondria are the primary site of reactive oxygen species (ROS) making them uniquely vulnerable to oxidative damage that may affect neuronal excitability and seizure susceptibility. This mini-review provides an overview of evidence suggesting the role of mitochondrial dysfunction and oxidative stress as acute consequences of injuries that are known to incite chronic epilepsy and their involvement in the chronic stages of acquired epilepsy.

O papel da dieta cetogênica no estresse oxidativo presente na epilepsia experimental

INTRODUÇÃO: A epilepsia é um dos transtornos neurológicos mais comuns, sendo definido como uma condição de crises recorrentes espontâneas. Existe uma importante relação entre radicais livres e enzimas antioxidantes no fenômeno epiléptico, e as espécies reativas de oxigênio (EROs) têm sido implicadas na neurodegeneração induzida pelas crises. OBJETIVO: A presente revisão teve como objetivo investigar a relação existente entre o estresse oxidativo e a epilepsia, destacando o efeito da dieta cetogênica sob condições experimentais. MATERIAL E MÉTODOS: Procedeu-se a pesquisa em artigos científicos publicados nos Bancos de Dados Medline, PubMed, Periódicos CAPES, ScienceDirect e Scielo. As palavras-chave selecionadas para a pesquisa incluíram epilepsia, status epilepticus, pilocarpina, estresse oxidativo, espécies reativas de oxigênio, disfunção mitocondrial. RESULTADOS E DISCUSSÃO: Terapia dietética tem sido utilizada, como é o caso da dieta cetogênica (DC), a qual é rica em lipídeos e pobre em carboidratos e utilizada por mais de oito décadas para o tratamento de epilepsia refratária, principalmente em crianças. A DC modula a bionergética mitocondrial, diminui a formação de EROs, aumenta a capacidade antioxidante celular e ainda, previne alterações do DNA mitocondrial. CONCLUSÃO: Evidências de atuação da DC na disfunção mitocondrial, como ocorre na epilepsia, são muitas e demonstram claramente efeitos benéficos dessa terapêutica.

Neurotoxins: free radical mechanisms and melatonin protection

Toxins that pass through the blood-brain barrier put neurons and glia in peril. The damage inflicted is usually a consequence of the ability of these toxic agents to induce free radical generation within cells but especially at the level of the mitochondria. The elevated production of oxygen and nitrogen-based radicals and related non-radical products leads to the oxidation of essential macromolecules including lipids, proteins and DNA. The resultant damage is referred to as oxidative and nitrosative stress and, when the molecular destruction is sufficiently severe, it causes apoptosis or necrosis of neurons and glia. Loss of brain cells compromises the functions of the central nervous system expressed as motor, sensory and cognitive deficits and psychological alterations. In this survey we summarize the publications related to the following neurotoxins and the protective actions of melatonin: aminolevulinic acid, cyanide, domoic acid, kainic acid, metals, methamphetamine, polychlorinated biphenyls, rotenone, toluene and 6-hydroxydopamine. Given the potent direct free radical scavenging activities of melatonin and its metabolites, their ability to indirectly stimulate antioxidative enzymes and their efficacy in reducing electron leakage from mitochondria, it would be expected that these molecules would protect the brain from oxidative and nitrosative molecular mutilation. The studies summarized in this review indicate that this is indeed the case, an action that is obviously assisted by the fact that melatonin readily crosses the blood brain barrier.

Mitochondria, oxidative stress, and temporal lobe epilepsy

Mitochondrial oxidative stress and dysfunction are contributing factors to various neurological disorders. Recently, there has been increasing evidence supporting the association between mitochondrial oxidative stress and epilepsy. Although certain inherited epilepsies are associated with mitochondrial dysfunction, little is known about its role in acquired epilepsies such as temporal lobe epilepsy (TLE). Mitochondrial oxidative stress and dysfunction are emerging as key factors that not only result from seizures, but may also contribute to epileptogenesis. The occurrence of epilepsy increases with age, and mitochondrial oxidative stress is a leading mechanism of aging and age-related degenerative disease, suggesting a further involvement of mitochondrial dysfunction in seizure generation. Mitochondria have critical cellular functions that influence neuronal excitability including production of adenosine triphosphate (ATP), fatty acid oxidation, control of apoptosis and necrosis, regulation of amino acid cycling, neurotransmitter biosynthesis, and regulation of cytosolic Ca(2+) homeostasis. Mitochondria are the primary site of reactive oxygen species (ROS) production making them uniquely vulnerable to oxidative stress and damage which can further affect cellular macromolecule function, the ability of the electron transport chain to produce ATP, antioxidant defenses, mitochondrial DNA stability, and synaptic glutamate homeostasis. Oxidative damage to one or more of these cellular targets may affect neuronal excitability and increase seizure susceptibility. The specific targeting of mitochondrial oxidative stress, dysfunction, and bioenergetics with pharmacological and non-pharmacological treatments may be a novel avenue for attenuating epileptogenesis.

Protective and antioxidative effects of GM1 ganglioside in PC12 cells exposed to hydrogen peroxide are mediated by Trk tyrosine kinase

GM1 ganglioside was found to increase the survival of PC12 cells exposed to H(2)O(2), its action was blocked by Trk tyrosine kinase inhibitor K-252a. Thus, the inhibition of H(2)O(2) cytotoxic action by GM1 constituted 52.8 +/- 4.3%, but in the presence of 1.0 microM K-252a it was only 11.7 +/- 10.8%, i.e. the effect of GM1 became insignificant. Exposure to GM1 markedly reduced the increased accumulation of reactive oxygen species (ROS) and diminished the inactivation of Na(+),K(+)-ATPase induced in PC12 cells by H(2)O(2), but in the presence of K-252a GM1 did not change these metabolic parameters. The inhibitors of extracellular signal-regulated protein kinase, phosphatidyl inositol 3-kinase and protein kinase C decreased the effects of GM1. A combination of these protein kinase inhibitors reduced inhibition of H(2)O(2) cytotoxic action by GM1 to the larger extent than each of the inhibitors and practically abolished the ability of GM1 to decrease H(2)O(2)-induced ROS accumulation. The protective and antioxidative effects of GM1 in PC12 cells exposed to H(2)O(2) appear to be mediated by activation of Trk receptor tyrosine kinase and the protein kinases downstream from this enzyme.

Protective role of endogenous gangliosides for lysosomal pathology in a cellular model of synucleinopathies

Gangliosides may be involved in the pathogenesis of Parkinson's disease and related disorders, although the precise mechanisms governing this involvement remain unknown. In this study, we determined whether changes in endogenous ganglioside levels affect lysosomal pathology in a cellular model of synucleinopathy. For this purpose, dementia with Lewy body-linked P123H beta-synuclein (beta-syn) neuroblastoma cells transfected with alpha-synuclein were used as a model system because these cells were characterized as having extensive formation of lysosomal inclusions bodies. Treatment of these cells with D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP), an inhibitor of glycosyl ceramide synthase, resulted in various features of lysosomal pathology, including compromised lysosomal activity, enhanced lysosomal membrane permeabilization, and increased cytotoxicity. Consistent with these findings, expression levels of lysosomal membrane proteins, ATP13A2 and LAMP-2, were significantly decreased, and electron microscopy demonstrated alterations in the lysosomal membrane structures. Furthermore, the accumulation of both P123H beta-syn and alpha-synuclein proteins was significant in PDMP-treated cells because of the suppressive effect of PDMP on the autophagy pathway. Finally, the detrimental effects of PDMP on lysosomal pathology were significantly ameliorated by the addition of gangliosides to the cultured cells. These data suggest that endogenous gangliosides may play protective roles against the lysosomal pathology of synucleinopathies.

Expression of ganglioside GT1b in mouse embryos at different developmental stages after cryopreservation

Gangliosides are a family of sialic acid-containing glycosphingolipids that are abundant in neurons and have a variety of functions in developing and mature tissues. We examined the expression of ganglioside GT1b in the embryonic preimplantation stage after freezing and thawing processes to determine the regulatory roles of ganglioside GT1b in early embryonic development. ICR mouse embryos at the two-cell stage obtained by flushing the oviducts were frozen by two cryopreservation procedures, slow freezing using a programmable freezer or vitrification by direct plunging into liquid nitrogen. Slow freezing was conducted with equilibration in 1.5 M 1,2-propanediol or 5% equilibration glycerol. Vitrification was applied with a 10-15 min equilibration in 7.5% ethylene glycol (EG), 7.5% dimethylsulfoxide (DMSO), and 30 sec in a solution of 15% EG, 15% DMSO and 0.5 M sucrose. Immediately after thawing, the survival rate of the embryos was assessed by their morphology and ability to develop to blastocysts in culture. The survival rate of vitrified and thawed embryos (92%) was significantly higher than that of slow frozen and thawed embryos (76%) (P<0.05). A tendency of higher blastocyst rate was found in the vitrified and thawed embryos compared to that of the slow frozen and thawed embryos. Confocal immunofluorescence staining confirmed that surviving embryos expressed ganglioside GT1b, with the strongest expression at the compacted eight-cell or later stage embryos. Ganglioside GT1b was not observed in the TUNEL-positive, apoptotic embryos, suggesting that cryopreservation had induced DNA breaks in them. These results suggest that ganglioside GT1b may play an important role in embryo survival or development.

Melatonin protects against MPTP/MPP+ -induced mitochondrial DNA oxidative damage in vivo and in vitro

The effects of melatonin on the mitochondrial DNA (mtDNA) damage induced by 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) and 1-methyl-4-phenylpyridine ion (MPP(+)) were investigated both in vivo and in vitro. MPTP (24 mg/kg, s.c.) induced a rapid increase in the immunoreactivity of 8-hydroxyguanine (8-oxoG), a common biomarker of DNA oxidative damage, in the cytoplasm of neurons in the Substantia Nigra Compact of mouse brain. Melatonin preinjection (7.5, 15 or 30 mg/kg, i.p.) dose-dependently prevented MPTP-induced DNA oxidative damage. In SH-SY5Y cells, MPP(+) (1 mm) increased the immunoreactivity of 8-oxoG in the mitochondria at 1 hr and in the nucleus at 3 hr after treatment. Melatonin (200 microm) preincubation significantly attenuated MPP(+)-induced mtDNA oxidative damage. Furthermore, MPP(+) time-dependently increased the accumulation of mitochondrial oxygen free radicals (mtOFR) from 1 to 24 hr and gradually decreased the mitochondrial membrane potential (Psim) from 18 to 36 hr after incubation. At 72 hr after incubation, MPP(+) caused cell death in 49% of the control. However, melatonin prevented MPP(+)-induced mtOFR generation and Psim collapse, and later cell death. The present results suggest that cytoprotection of melatonin against MPTP/MPP(+)-induced cell death may be associated with the attenuation of mtDNA oxidative damage via inhibition of mtOFR generation and the prevention of Psim collapse.

When melatonin gets on your nerves: its beneficial actions in experimental models of stroke

This article summarizes the evidence that endogenously produced and exogenously administered melatonin reduces the degree of tissue damage and limits the biobehavioral deficits associated with experimental models of ischemia/reperfusion injury in the brain (i.e., stroke). Melatonin's efficacy in curtailing neural damage under conditions of transitory interruption of the blood supply to the brain has been documented in models of both focal and global ischemia. In these studies many indices have been shown to be improved as a consequence of melatonin treatment. For example, when given at the time of ischemia or reperfusion onset, melatonin reduces neurophysiological deficits, infarct volume, the degree of neural edema, lipid peroxidation, protein carbonyls, DNA damage, neuron and glial loss, and death of the animals. Melatonin's protective actions against these adverse changes are believed to stem from its direct free radical scavenging and indirect antioxidant activities, possibly from its ability to limit free radical generation at the mitochondrial level and because of yet-undefined functions. Considering its high efficacy in overcoming much of the damage associated with ischemia/reperfusion injury, not only in the brain but in other organs as well, its use in clinical trials for the purpose of improving stroke outcome should be seriously considered.

Melatonin mitigates mitochondrial malfunction

Melatonin, or N-acetyl-5-methoxytryptamine, is a compound derived from tryptophan that is found in all organisms from unicells to vertebrates. This indoleamine may act as a protective agent in disease conditions such as Parkinson's, Alzheimer's, aging, sepsis and other disorders including ischemia/reperfusion. In addition, melatonin has been proposed as a drug for the treatment of cancer. These disorders have in common a dysfunction of the apoptotic program. Thus, while defects which reduce apoptotic processes can exaggerate cancer, neurodegenerative disorders and ischemic conditions are made worse by enhanced apoptosis. The mechanism by which melatonin controls cell death is not entirely known. Recently, mitochondria, which are implicated in the intrinsic pathway of apoptosis, have been identified as a target for melatonin actions. It is known that melatonin scavenges oxygen and nitrogen-based reactants generated in mitochondria. This limits the loss of the intramitochondrial glutathione and lowers mitochondrial protein damage, improving electron transport chain (ETC) activity and reducing mtDNA damage. Melatonin also increases the activity of the complex I and complex IV of the ETC, thereby improving mitochondrial respiration and increasing ATP synthesis under normal and stressful conditions. These effects reflect the ability of melatonin to reduce the harmful reduction in the mitochondrial membrane potential that may trigger mitochondrial transition pore (MTP) opening and the apoptotic cascade. In addition, a reported direct action of melatonin in the control of currents through the MTP opens a new perspective in the understanding of the regulation of apoptotic cell death by the indoleamine.

Reduction of oxidative changes in human spermatozoa by exogenous gangliosides

The effect of exogenous gangliosides, the sialic acid-containing glycosphingolipids, on oxidative changes in human spermatozoa was investigated. The incorporation of disialogangliosides or trisialogangliosides (GD1b and GT1b, respectively) into the iron/ascorbate promoter system for induction of lipid peroxidation decreased the release of malondialdehyde (MDA) from peroxidizing spermatozoa. The application of monosialogangliosides and disialogangliosides (GM1 and GD1a, respectively) did not have any effect under identical experimental conditions. GT1b, at a micromolar concentration, significantly inhibited the production of MDA, a breakdown product of lipid peroxide decomposition in spermatozoa of normozoospermic infertile men (P < 0.001; n = 51). An enhanced generation of MDA exhibited by the sperm population from the low-density Percoll fraction containing defective and/or immature spermatozoa was significantly reduced in the presence of GT1b. These results and the experiments on the influence of iron-chelating agent ethylenediamine tetraacetic acid (EDTA) as well as ferrous ion concentration itself on lipid peroxidation support the hypothesis that the protective effect of ganglioside against MDA generation could be the result of its chelating activity. Furthermore, superoxide anion release of phorbol myristate acetate-stimulated spermatozoa was significantly reduced in the presence of 50 and 100 micromol l(-1) GD1b (P < 0.05) and GT1b (P < 0.005). The inhibitory effect of 100 micromol l(-1) GT1b on spermatozoa from infertile normozoospermic men was statistically significant (P < 0.001; n = 21) and did not depend on the initial superoxide anion production. In conclusion, the protective action of GD1b and GT1b could be related to both scavenging of free radicals and metal-chelating properties, which might have relevance in the protection against oxidation-induced processes in human spermatozoa.

Melatonin and mitochondrial function

Melatonin is a natural occurring compound with well-known antioxidant properties. In the last decade a new effect of melatonin on mitochondrial homeostasis has been discovered and, although the exact molecular mechanism for this effect remains unknown, it may explain, at least in part, the protective properties found for the indoleamine in degenerative conditions such as aging as well as Parkinson's disease, Alzheimer's disease, epilepsy, sepsis and other injuries such as ischemia-reperfusion. A common feature in these diseases is the existence of mitochondrial damage due to oxidative stress, which may lead to a decrease in the activities of mitochondrial complexes and ATP production, and, as a consequence, a further increase in free radical generation. A vicious cycle thus results under these conditions of oxidative stress with the final consequence being cell death by necrosis or apoptosis. Melatonin is able of directly scavenging a variety of toxic oxygen and nitrogen-based reactants, stimulates antioxidative enzymes, increases the efficiency of the electron transport chain thereby limiting electron leakage and free radical generation, and promotes ATP synthesis. Via these actions, melatonin preserves the integrity of the mitochondria and helps to maintain cell functions and survival.

Effect of alpha-ketoglutarate and oxaloacetate on brain mitochondrial DNA damage and seizures induced by kainic acid in mice

The effects of alpha-ketoglutarate and oxaloacetate on brain mitochondrial DNA (mtDNA) damage and seizures induced by kainic acid were examined both in vivo and in vitro. An intraperitoneal (ip) injection of kainic acid (45 mg/kg) produced broad-spectrum limbic and severe sustained seizures in all of the treated mice. The seizures were abolished when alpha-ketoglutarate (2 g/kg) or oxaloacetate (1 g/kg) was injected intraperitoneally in the animals 1 min before kainic acid administration. In addition, the administration of kainic acid caused damage to mtDNA in brain frontal and middle cortex of mice. These effects were completely abolished by the ip preinjection of alpha-ketoglutarate (2 g/kg) or oxaloacetate (1 g/kg). In vitro exposure of kainic acid (0.25, 0.5 or 1.0 mM) to brain homogenate inflicted damage to mtDNA in a concentration-dependent manner. The damage of mtDNA induced by 1.0 mM kainic acid was attenuated by the co-treatment with alpha-ketoglutarate (2.5 or 5.0 mM) or oxaloacetate (0.75 or 1.0 mM). Furthermore, in vivo and in vitro exposure of kainic acid elicited an increase in lipid peroxidation. However, the increased lipid peroxidation was completely inhibited by cotreatment of alpha-ketoglutarate or oxaloacetate. These results suggest that alpha-keto acids such as alpha-ketoglutarate and oxaloacetate play a role in the inhibition of seizures and subsequent mtDNA damage induced by the excitotoxic/neurotoxic agent, kainic acid.